The present invention relates to a capacitor and more particularly, to a variable capacitor for use in electrical and electronic equipment.
Recently, variable capacitors, especially those of extremely small sizes and yet having sufficiently large electrostatic capacity have come into wide use in various fields of electrical and electronic industries, following the miniaturization of circuit constructions of electrical and electronic equipment.
Referring to FIG. 1, there is shown one example of such conventional variable capacitors which comprises a stator S having a stator electrode Se which is formed on the upper surface thereof with suitable electrode material through baking or coating. A rotor R is rotatably disposed on the stator electrode Se and fixed, for example, by soldering to a rotary shaft A for rotation therewith. A rotor electrode Re is formed in the recess at the upper surface of the rotor R through baking or coating of suitable electrode material. In addition, a rotor terminal lead Rt having a resilient plate spring portion Rt1 extends over the under surface of the stator S and includes a terminal end Rt2 which extends downwardly from the spring portion Rt1. Further, a stator terminal lead St soldered at an upper end thereof to the stator S and extends downwardly through the stator S. The lower end of the rotary shaft A extends through the resilient spring portion Rt1 of the rotor terminal lead Rt and is staked thereat as shown.
Referring also to FIG. 2, the conventional variable capacitors of the above described type have various disadvantages in that if the capacitor itself is of small size, the width l of the recess formed in the upper surface of the rotor R is limited in length, therefore making it impossible for the rotor electrode Re to have a sufficiently large area. In addition, the thickness t between the rotor electrode Re and the under surface of the rotor R can not be made small enough from the viewpoint of maintaining strength of the rotor R itself. From such restrictions, it is quite difficult to provide the variable capacitors of known constructions with large electrostatic capacity. Furthermore, in the conventional variable capacitors of the above described type, troublesome procedures for the electrode formation and soldering are inevitably involved, thus it is difficult to save labor in the manufacturing processes. This results in consequently higher cost and increased probability of producing faulty products. In addition, since the rotor R is exposed, the same rotor R is liable to be damaged, especially at the electrode Re thereof, during transit or incorporation into the circuit of a particular piece of equipment. Further, since the variable capacitor can not be placed in close contact with other components, miniaturization of the equipment itself is hard to be achieved, while the variable capacitor itself tends to be affected by dust and dirt.